Method of automatically rotating a hollow shell in a plug mill

ABSTRACT

In a plug mill following a Mannesmann piercing mill on a seamless tube production line, a method whereby the rolled hollow shell which has been subjected to the first rolling pass is automatically rotated about its longitudinal central axis by an angle of about 90* while it is being returned to the inlet Vtable of the plug mill for the second rolling pass.

United States Patent [191 Kamimura et al.

[4 1 Oct. 14, 1975 METHOD OF AUTOMATICALLY ROTATING A HOLLOW SHELL IN APLUG MILL [75] Inventors: Haruo Kamimura, Yokohama;

Toshitsugu Nakai, Tokyo; Katsumi Wadano, Yokohama, all of Japan [73]Assignee: Nippon Kokan Kabushiki Kaisha,

Tokyo, Japan [22] Filed: Aug. 1, 1974 [21] App]. No.: 493,782

[30] Foreign Application Priority Data Aug. 23, 1973 Japan 48-93859 [52]US. Cl. 72/209; 72/251; 72/247 [51] Int. Cl. ..B21B 17/12; 8218 39/16;B21B 39/26 [58] Field of Search 72/251, 209, 250, 247, 72/229-231 [56]References Cited UNITED STATES PATENTS 9,274 9/1852 Knight 72/247662,916 12/1900 Daschbach.... 72/251 1,928,811 lO/1933 Burns 72/2512,016,141 10/1935 Geer...'. 72/231 Primary ExaminerMi1ton S. MehrAttorney, Agent, or FirmFlynn & Frishauf [57] ABSTRACT In a plug millfollowing a Mannesmann piercing mill on a seamless tube production line,a method whereby the rolled hollow shell which has been subjected to thefirst rolling pass is automatically rotated about its longitudinalcentral axis by an angle of about 90 while it is being returned to theinlet. V-table of the plug mill for the second rolling pass.-

11 Claims, 5 Drawing Figures U.S. Patent Oct. 14, 1975 Sheet 1 on3,911,714

- 7 r= g 3 i ll 8 IO Llr U.S. Patent Oct. 14, 1975 Sheet 2 of2 3,911,714

METHOD OFAUTOMATICALLY ROTATING A HOLLOW SHELL IN A PLUG MILL BACKGROUNDOF THE INVENTION The present invention relates to a method whereby in aplug mill following a Mannessmann piercing mill on a seamless tubeproduction line, the rolled hollow shell which has been subjected to thefirst rolling pass thus having fin-like sides in section, is rotatedabout its longitudinal central axis by an angle of about 90before I thesecond rolling pass which is effected using the same 'roll calibers andreplacing only the plug with another plug. In the description of thisspecification, the roll caliber means the shape of the grooves in eachof the pair of opposed work rolls in the plug mill.

In the conventional plug mill, the bottom roll of the pair of returnrolls of a return roll means located to the rear of the plug mill havinga pair of work rolls is in its lowered position during the rollingoperation of the plug mill. When the first rolling pass is over and therolled hollow shell is to be returned to the inlet V-table for thesecond rolling pass, the top work roll of the plug mill is elevated andthe bottom return roll of the return roll means is elevated by a liftingmechanism. Consequently, the rolled hollow shell is gripped firmlybetween the pair of return rolls so that the rotation of the returnrolls returns the rolled hollow shell to the inlet V-table of the plugmill. However, since the roll caliber in each of the top and bottom workrolls of the plug mill is made circular onlywith respect to about 120 ofits center angle and the remaining angular portions each have a reliefformed therein to facilitate the rolling operation, these reliefportions produce during the first rolling pass fins on both sides of thehollow shell which make the wall thickness of the shell nonuniform, andtherefore it is necessary to rotate the rolled hollow shell by an angleof 90 before the second rolling pass is started so that the fin portionsof the rolled hollow shell are rolled during the second rolling pass toprovide a uniform wall thickness by the second rolling pass.

While the rotation of such a rolled hollow shell is accomplished bymeans of various methods including manual methods, manual methodsassisted by mechanical powerv and methods employing only mechanicalpower under electrical controls, these conventional methods respectivelyhave their own advantages and disadvantages.

SUMMARY OF THE INVENTION In the light of the foregoing prior art, it isan object of the present invention to provide a method of automaticallyrotating the rolled hollow shell in a plug mill wherein in contrast tothe conventional methods in which the rolled hollow shell subjected tothe'first rolling pass in the plug mill is rotated after it hasbeen'returned to the inlet V-table of the plug mill by its return rollmeans, the rolled hollow shell is automatically rotated during itsreturn stroke by the return roll means, resulting in lessening of therequired work, reduced rolling cycle time and improved rollingefficiency.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a general plan view showinga plug mill and return roll means as well as associated tables;

FIG. 2 is a front elevation showing the return roll means of FIG. 1comprising a pair of rolls as viewed in the direction of the arrow IIII;

FIG. 3 is a schematic view showing the manner in which the matching rollcalibers of the top and bottom return rolls of said return roll meansare shifted relative to each other;

FIG. 4 is a sectional view showing an exemplary form of the non-drivenside bearing section of the top return roll of said return r'oll means;and

FIG. 5 is a sectional view showing an exemplary form of the non-drivenside bearing section of the bottom return roll of said return rollmeans.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIG. 1showing the arrangement of a plug mill, return roll means 7 and an inletV-table 3, a material converted into a hollow shell 1 by a Mannessmannpiercing mill (not shown) is kicked out onto inclined skid rails 2, andthe hollow shell 1 is moved forward while rolling over the inclined skidrails 2. After the hollow shell 1 has eventually fallen into an inletV-table 3, the hollow shell 1 is pushed forward longitudinally and fedbetween top and bottom work rolls of the plug mill 5 by a pusher 4, andit is then subjected to the first rolling pass in the plug mill 5. Abottom return roll 9 of return roll means 7 is held in its loweredposition during thefirst rolling pass of the plug roll mill 5 and assoon as the first rolling pass is over, the bottom return roll 9 of thereturn roll means 7 is elevated and the rolled hollow shell 1 is grippedby the top and bottom return rolls 8 and 9 which are then rotated tofeed the rolled hollow shell 1 back to the inlet V-table 3 through thetop and bottom work rolls of the plugmill 5. In this case, the rolledhollow shell I is not affected by the plug mill 5, since its top workroll is in its elevated position. The rolled hollow shell is againpushed forward by the pusher 4 and it is fed to the plug mill 5 for thesecond rolling pass.

The automatic rotation by of a rolled hollow shell according to thepresent invention is accomplished during the return stroke when therolled hollow shell that has been subjected to the first rolling pass isreturned to the inlet \/-table 3 by the return roll means 7. In FIG. 2,the return roll means 7 automatically rotates the rolled hollow shellabout 90 during its return stroke by means of its special structureincluding a nondriven side bearing section 10 on one end of the shaft ofthe top return roll 8 and a driven side bearing section 11 on the otherend thereof, and a non-driven thrust locking mechanism 12 of the bottomreturn roll 9 for preventing the movement of the roll 9 in the directionof the center line of its shaft. In the non-driven side bearing section10, as shown in FIG. 4, a roll shaft 17 of the top return roll 8 ismounted in roll-neck bearings 13 which are mounted in a bearing chock14. The rollneck bearings 13 consist of needle bearings, thus permittingthe axial movement of the roll shaft 17. A pusherplate 16 formed with athreaded hole in the central portion thereof is provided on the outsideof the bearing chock 14 on itscenter line, and a screw shaft push rod 15having a rotary center at one end thereof and a square turning head atthe other end thereof is threadedly mounted in the threaded hole of thepusher plate 16 to move the roll shaft 17 and hence the top return roll8 in the axial direction by the turning of the square head. Although notshown in the drawings, the driven side bearing sections 11 and 6 employneedle bearings to permit the axial movement of the associated rollshafts. The roll shaft of the bottom return roll 9 is mounted, as shownin FIG. 5, in thrust bearings 18 and 19 of the thrust locking mechanism12 for exerting a thrust in the direction of the center line of thebottom return roll shaft, and in this way the axial movement of thebottom return roll 9 is prevented. It should be noted that it ispossible to arrange the component elements of the above-describedautomatic shell rotating mechanism in an inverse relation relative tothe top and bottom return rolls to obtain the same results.

In operation, if the screw shaft push rod 15 is turned so.that the rollshaft 17 of the upper return roll 8 is moved slightly and the matchingcalibers of the top and bottom rolls 8 and 9 in the return roll means 7are slightly displaced from each other (by a displacement amount A) asshown in FIG. 3, a turning moment acts on the rolled hollow shell whichrotates in a direction in which the peripheral speed of the contactingrolls is great, i.e., in the clockwise direction in FIG. 3. Therefore,by suitably selecting the displacement amount A (the value of A is inthe range 2-1 5 m/m and preferably on the order of several m/m) inconsideration of various factors such as the diameter and length of atube to be produced, the rolled hollow shell that has been subjected tothe first rolling pass can be rotated during its return stroke to theinlet V-table so that the horizontal fin-like portions of the shell areplaced in the desired vertical positions. The following example showsthe results obtained in accordance with the method of this invention.

1. The dimensions of the tube produced: l39.7 outside diameter X 7.72wall thickness X 10,200 length (mm) 2. Rolling plan: Dimensions afterthe first plug mill rolling pass-I47 outside diameter X 7.9 wallthickness X 10,200 length (mm) (3) Details of the example:

Details of return roll means:

90 degrees flO degrees 9.6 (m/sec) 1.9 (sec) 47.4 (degree/sec) Degree ofshell rotation Return stroke speed Return stroke time Rotational speedlt will be seen from the above data that the desired results wereaccomplished.

While, in the above described example, the top and bottom return rolls 8and 9 were slightly slid or displaced axially relative to each other toexert a turning moment on the rolled hollow shell, it is obvious tothose skilled in the art without any detailed description that the rollshafts of the top and bottom return rolls 8 and 9 may be arranged asshown by the dot and chain lines in FIG. 1 so that the roll shafts crosseach other at small angles at the center of the roll calibers throughwhich the rolled hollow shell is passed so as to similarly exert aturning moment on the rolled hollow shell. Suitably, this crossing anglea is in the range 1 to 5.

Therefore, it is also possible to rotate the rolled hollow shell byslightly displacing the matching calibers of the top and bottom returnrolls 8 and 9 of the return roll means 7 from each other as in theabove-described embodiment and by further intersecting the top andbottom return roll shafts at small angles at the center of the rollcalibers through which the rolled hollow shell is passed.

It will thus be seen from the foregoing description that according tothis invention, the matching roll calibers of the top and bottom returnrolls 8 and 9 of the return roll means 7 may be displaced from eachother by an amount A, or the roll shafts of the top and bottom returnrolls 8 and 9 may be arranged to cross each other at small angles at thecenter of the roll calibers through which the rolled hollow shell ispassed, or both of these methods may be employed together so that thecontacting time between the top and bottom return rolls 8 and 9 of thereturn roll means 7 is controlled by means of a timer or the like toautomatically rotate the rolled hollow shell by an angle ofpredetermined degrees during its return stroke to the inlet side of theplug mill. Further, it is possible to use additional methods such asincreasing the relief portion R in each of the matching top and bottomreturn roll calibers to ensure a smooth automatic rotation of the rolledhollow shell or increasing the relief portion to amount to about onehalf of each of the matching top and bottom return roll calibers so thatthe fin portions of the rolled hollow shell do not impede in any way theautomatic rotation of the rolled hollow shell. Thus, the presentinvention has among its great advantages the fact that with only asimple modification of the conventional equipment, it is possible tolessen the amount of work required for the rolling operation of tubesand thereby to ensure an increased industrial utility of the invention.

We claim:

1. In a tubular product production line including a plug mill, feedmeans for feeding the product to said plug mill, and return means forreturning a rolled hollow shell that has been subjected to a rollingpass in said plug mill to said feed means, said return means including apair of rotatable return rolls located at the outlet side of said plugmill, a rolling method comprisfeeding a tube to said plug mill;

rolling said tube in said plug mill; and

engaging said rolled tube fed out from said plug mill with said pair ofreturn rolls, and rotating said return rolls to return said engagedrolled tube back to said feed means while rotating said rolled tube bysaid return rolls by an angle of about degrees around the longitudinalcentral axis of said rolled tube before said rolled tube is fed to saidplug mill for a second rolling pass.

2. In the method according to claim 1, wherein said return rolls havematching opposing calibers for engaging said rolled tube therebetween,said calibers being displaced by a fixed distance relative to each otherin the direction of the axes of rotation of said return rolls, whereby aturning moment is imparted to said rolled tube passing through said rollcalibers upon rotation of said return rolls.

3. In the method according to claim 2 wherein said rotating stepcomprises rotatably driving at least one of said rolls.

4. In the method according to claim 2 wherein said return rolls arerespectively located above and below said rolled tube.

5. In the method according to claim 1, wherein said return rolls havematching opposed calibers for engaging said rolled tube therebetween,comprising orienting said rolls such that the longitudinal axes ofrotation of said pair of return rolls cross each other in terms of theplan view substantially at the center of said matching roll calibersbetween which said rolled tube is passed, whereby a turning moment isapplied to said rolled tube passing through said roll calibers uponrotation of said return rolls.

6. The method according to claim 5 wherein said rotating step comprisesrotatably driving at least one of said rolls.

7. The method according to claim 5 wherein said return rolls arerespectively located above and below said rolled tube.

8. In the method according to claim 5, wherein said matching rollcalibers of said pair of return rolls are further slightly displacedfrom each other substantially in the direction of the axes of rotationthereof.

9. In the method according to claim 1, wherein said return rolls arerespectively located above and below said rolled tube, said bottomreturn roll being fixed and said top return roll being displaced in thelongitudinal axial direction thereof.

10. In the method according to claim 1, Wherehi said return rolls arerespectively located above and below said rolled tube, said top returnroll being fixedand said bottom return roll being displaced in thelongiiudjnal axial direction thereof.

11. In the method according to claim 1, wherein said return rolls arerespectively located above and below said rolled tube, at least one ofsaid retum'rnlrls being displacable in a direction toward and away fromsaid rolled tube, and wherein said at least one displacable roll isdisplaced away from said rolled tube-during said feeding and rollingstep, said at least onedisplacable roll thereafter being displacedtoward said rolled tube to engage said rolled tube for returntlrereofback to said feeding means.

1. In a tubular product production line including a plug mill, feedmeans for feeding the product to said plug mill, and return means forreturning a rolled hollow shell that has been subjected to a rollingpass in said plug mill to said feed means, said return means including apair of rotatable return rolls located at the outlet side of said plugmill, a rolling method comprising: feeding a tube to said plug mill;rolling said tube in said plug mill; and engaging said rolled tube fedout from said plug mill with said pair of return rolls, and rotatingsaid return rolls to return said engaged rolled tube back to said feedmeans while rotating said rolled tube by said return rolls by an angleof about 90 degrees around the longitudinal central axis of said rolledtube before said rolled tube is fed to said plug mill for a secondrolling pass.
 2. In the method according to claim 1, wherein said returnrolls have matching opposing calibers for engaging said rolled tubetherebetween, said calibers being displaced by a fixed distance relativeto each other in the direction of the axes of rotation of said returnrolls, whereby a turning moment is imparted to said rolled tube passingthrough said roll calibers upon rotation of said return rolls.
 3. In themethod according to claim 2 wherein said rotating step comprisesrotatably driving at least one of said rolls.
 4. In the method accordingto claim 2 wherein said return rolls are respectively located above andbelow said rolled tube.
 5. In the method according to claim 1, whereinsaid return rolls have matching opposed calibers for engaging saidrolled tube therebetween, comprising orienting said rolls such that thelongitudinal axes of rotation of said pair of return rolls cross eachother in terms of the plan view substantially at the center of saidmatching roll calibers between which said rolled tube is passed, wherebya turning moment is applied to said rolled tube passing through saidroll calibers upon rotation of said return rolls.
 6. The methodaccording to claim 5 wherein said rotating step comprises rotatablydriving at least one of said rolls.
 7. The method according to claim 5wherein said return rolls are respectively located above and below saidrolled tube.
 8. In the method according to claim 5, wherein saidmatching roll calibers of said pair of return rolls are further slightlydisplaced from each other substantially in the direction of the axes ofrotation thereof.
 9. In the method according to claim 1, wherein saidreturn rolls are respectively located above and below said rolled tube,said bottom return roll being fixed and said top return roll beingdisplaced in the longitudinal axial direction thereof.
 10. In the methodaccording to claIm 1, wherein said return rolls are respectively locatedabove and below said rolled tube, said top return roll being fixed andsaid bottom return roll being displaced in the longitudinal axialdirection thereof.
 11. In the method according to claim 1, wherein saidreturn rolls are respectively located above and below said rolled tube,at least one of said return rolls being displacable in a directiontoward and away from said rolled tube, and wherein said at least onedisplacable roll is displaced away from said rolled tube during saidfeeding and rolling step, said at least one displacable roll thereafterbeing displaced toward said rolled tube to engage said rolled tube forreturn thereof back to said feeding means.